[HECnet] OpenVMS 6.1 Cluster - Alpha not booting to form cluster

[Brian Schenkenberger, VAXman-]

Mark Wickens <mark at wickensonline.co.uk> writes:

On 08/10/2013 12:15, Brian Schenkenberger, VAXman- wrote:
Mark Wickens <mark at wickensonline.co.uk> writes:

On 08/10/2013 11:33, Brian Schenkenberger, VAXman- wrote:
Mark Wickens <mark at wickensonline.co.uk> writes:

Just wondered if anyone would know why my Alpha when booting hangs at
the point where it attempting to determine whether to join or form a VMS
cluster? It is clustered with a VAX - if I boot the VAX first the VAX
creates a cluster which the Alpha will then happily join when turned on,
but if I power the Alpha without the VAX it just hangs.

Both are running an install straight from an original VMS 6.1
installation disk.
Just 2 nodes?

What's your quorum configuration?

Post:

$ MCR SYSGEN SHOW VOTES
$ MCR SYSGEN SHOW EXPECTED_VOTES

..from each node.
I think you, sir, may have found the issue:

On RIPLEY (the Alpha):

$ mcr sysgen show votes
Parameter Name                       Current       Default         Min.         Max. Unit   Dynamic
--------------                       -------       -------       -------   ------- ----
-------
VOTES                                                     1                   1                 0             127 Votes
$ mcr sysgen show expected votes
Parameter Name                       Current       Default         Min.         Max. Unit   Dynamic
--------------                       -------       -------       -------   ------- ----
-------
EXPECTED_VOTES                                   2                   1                 1             127 Votes


On DALLAS (the VAX):

$ mcr sysgen show votes
Parameter Name                       Current       Default         Min.         Max. Unit   Dynamic
--------------                       -------       -------       -------   ------- ----
-------
VOTES                                                     1                   1                 0             127 Votes
$ mcr sysgen show expected votes
Parameter Name                       Current       Default         Min.         Max. Unit   Dynamic
--------------                       -------       -------       -------   ------- ----
-------
EXPECTED_VOTES                                   1                   1                 1             127 Votes

OK.   First, 2 node clusters can be problematic due to not realy having the
necessary number of node to properly form a cluster.   The minimum is three
nodes to form a cluster.

However, let's look at what you said.

You said that the VAX boots and forms a cluster.   It has one vote and the
expected votes is one.   Therefore, when you boot it, it sees the necessary
number of votes to continue booting and form a cluster.

You also said that Alpha boots and hangs trying to form a cluster.   It too
has one vote but its expected votes is two.   Therefore, until the VAX has
booted, the number of votes is not present and the Alpha will hang.

If you lower expected votes, the Alpha wil boot just like the VAX does.   I
would caution you read the VMS documentation regarding clusters and how to
determine quorum.   You risk, in the configuration of two nodes where each
has one vote and expected votes of one, partitioning the cluster resulting
in data corruption.

Thanks for the reminder of these issues. To be honest my experience with 
clustering is limited and generally specific to satellite based 
configurations. In this case I may make the VAX a satellite of the Alpha 
with the local disk acting as page/swap.

Am I right in thinking then that the relationship changes somewhat in 
that the Alpha will always need to be up but the VAX can come and go as 
it pleases (with the correct shutdown sequence)?

All nodes:	EXPECTED_VOTES = 1
Alpha:		VOTES = 1
VAX/satellites:	VOTES = 0

The VAX and any satellites can come and go.   You may see some delay on
the Alpha as these transitions occur.

-- 
VAXman- A Bored Certified VMS Kernel Mode Hacker       VAXman(at)TMESIS(dot)ORG

Well I speak to machines with the voice of humanity.